Steel power transmission poles have steel arms to support electric conductors. The steel arms are often tubular in cross section with varying lengths that may reach 20 feet or greater. The steel arms project horizontally from the steel poles. The steel poles also have shorter steel arms, typically located at the very top of the pole, to support the ground wires, also referred to as the shield or static wire arms. Each of the steel arms is made of a steel shell (tube) and has a hollow interior. The steel arms are welded to a bracket, which is then bolted to steel plates that are welded to the steel pole. The tubular steel arms can be tapered or non-tapered.
Wind loads on these arms can cause the arms to vibrate. The repeated flexing at the welded joint creates fatigue stresses, which may cause fatigue cracking at the welded joint. In order to address this problem, the practice has been to secure the arms to the pole with tie down cables immediately upon installation. Also, the specifications for welding the arms to the brackets require a substantial weld which requires a substantial expenditure of time and material for the welding process.